Much like the original Portal, Portal 2 is a very simple game at its core. However, there are far more testing elements here than there were in the first game. It is vital to have at least a basic understanding of how each element works in order to complete the test chambers.
Aperture Science Handheld Portal Device[edit]
As with the original Portal, the Portal Device (or "portal gun", as it is commonly referred to) is the only object in the game that you have direct conrol of. However, using it effectively is the most vital skill you can learn. The portals it creates will be your primary means of moving about the test chambers and manipulating the various elements within. By default, 
will create the blue end of a portal, and 
will create the orange end.
Portals[edit]
Everything revolves around portals. They allow you to easily move to otherwise inaccessible areas and manipulate testing elements that would otherwise serve no purpose. Early in the game, portals are pre-made, but once you acquire the portal gun, you can create your own portals. However, not all surfaces can accept a portal, and learning which surfaces can and cannot is vital to your success. The general rule of thumb is that portalable surfaces are some shade of white, whereas nonportalable surfaces are generally darker. Portals of two colors can exist at any given time: blue and orange. Anything that passes through a blue portal will come out of the orange portal, and vice versa. One of the key skills that must be acquired with using portals is that of flinging. "Flinging" refers to entering one portal at high speeds (usually by falling into it from a great height) to propel out the other. Because momentum is conserved between portals, this technique can be used to reach otherwise inaccessible areas which lack portalable surfaces.
Material Emancipation Grilles[edit]
Material Emancipation Grilles, commonly known as fizzlers, serve three primary functions. The first is to vaporize any testing objects that pass through them, such as cubes and turrets. Second, any previously-placed portals will vanish when passing through a fizzler. Third, portals cannot be shot through fizzlers. While their most common placement is in front of Chamberlocks at the end of each test chamber, they are also frequently used as puzzle elements, with the primary goal being to somehow get a portal or a testing object past them.
Weighted Storage Cubes[edit]
These handy little boxes can be used for a variety of purposes, including (but not limited to) holding down buttons, blocking lasers, and disabling turrets. A new feature of the Weighted Storage Cube is that the blue ring in the center of the cube will turn orange while resting on a button, thus giving a clear sign that it is, in fact, holding the button down. In co-op mode, Weighted Storage Cubes are frequently replaced by Edgless Safety Cubes, which are basically cubes in spherical form. In Chapter 8's test chambers, these cubes will be replaced with Frankenturrets, a madman's mashing together of Weighted Storage Cubes and turrets. The primary difference between a regular cube and a Frankenturret is that, if set down in a specific manner, Frankenturrets will start to hobble around. Keep that in mind when placing them on buttons, as they have a tendency to wander off of them if left to their own devices.
Buttons[edit]
Buttons come in two varieties. Buttons mounted on podiums activate certain test elements and are often run on timers. Buttons mounted on floors, walls, and ceilings must be held down in order for their effects to activate. The only things heavy enough to hold down one of these buttons are you and cubes. Sometimes, these buttons are specifically shaped to only accept a cube, so keep on the lookout for them.
Thermal Discouragement Beams[edit]
An introduction to Thermal Discouragement Beams.
The first new testing element in Portal 2, Thermal Discouragement Beams, henceforth referred to as lasers, serve two primary purposes. The first is to activate receptacles, and the second is to destroy turrets. While simply touching a laser isn't enough to outright kill you, touching one for extended periods of time will, so be careful. Note that, unlike other objects, lasers can pass through glass walls unimpeded, and a few puzzles make use of this special property.
Thermal Discouragement Beam Receptacles[edit]
These are the targets at which you should aim lasers. They come in two varieties. Wall-mounted receptacles are the ultimate goal of any laser, while floor- and ceiling-mounted receptacles allow lasers to pass through them. When the latter appear, your goal will often be to make the laser pass through all of them at once, with the laser usually ending up at a wall-mounted receptacle. However, not always will you want a laser to reach a receptacle. Sometimes laser receptacles will affect the test area in undesirable ways; in these cases, your goal will be to block the laser from reaching the receptacle, usually with cubes.
Thermal Redirection Cubes[edit]
Thermal Redirection Cubes are just like regular cubes, with one exception: it has the ability to refract and redirect any laser that hits it. This will allow you to guide lasers to receptacles when using portals is not an option. Oftentimes, puzzles will require you to use redirection cubes and portals in conjunction to allow the laser to travel long distances or in otherwise impossible ways.
Aerial Faith Plate[edit]
An introduction to Aerial Faith Plates.
The purpose of the Aerial Faith Plate is to launch you and/or other objects long distances. Oftentimes, in rooms with faith plates, you will see a target on the wall or floor. These targets serve to denote where the faith plate will launch you to. Oftentimes faith plates can be used to give you the proper momentum to fling in areas where there is no place to fall.
Hard Light Bridges[edit]
The primary purpose of the Hard Light Bridge is to provide a portable floor with which to cross large chasms or to catch cubes that would otherwise fall into a pit or pool of water. Another function of the Hard Light Bridge is to create walls in front of turrets, blocking you from their line of fire. In coop mode, you and your partner will often be reqired to chain both sets of portals together in order to extend light bridges to places they otherwise wouldn't be able to reach.
Excursion Funnels[edit]
An introduction to Excursion Funnels.
When you or any object enter an Excursion Funnel, you will float inside it until you choose to exit it. Note that while inside a funnel, you cannot move in the direction opposite the funnel's flow. Some buttons in rooms with funnels will reverse the funnel's flow, so that instead of moving away from the funnel's source, it moves towards it. When this happens, the funnel's color will change from blue to orange. Much like with Light Bridges, co-op puzzles with Excursion Funnels will often require portal chaining to redirect the funnel's flow multiple times.
Repulsion Gel[edit]
An introduction to Repulsion Gel.
Anything that comes into contact with this blue gel will instantly bounce off of it like rubber. The gel can cover any solid surface (but not grated surfaces). When bouncing off of floors, you will bounce at the same height you fell from, so keep that in mind when trying to reach high-up areas. If you don't want to bounce, you can crouch to cancel the gel's effects. In addition to using it to bounce off of floors, you can also coat opposing walls with the gel, enabling you to bounce between them and cross large chasms. If the gel covers an object, that object will start to bounce around uncontrollably; this property can be used as an effective (and fun) way to disable turrets.
Propulsion Gel[edit]
An introduction to Propulsion Gel.
Running on any surface covered with this red gel will greatly increase your speed. This can be used to two ends: to propel yourself off of ramps, or to use it as another means of gaining momentum for flinging (allowing you to fling through walls instead of floors). Unlike the other two gels, propulsion gel on walls and ceilings have no effect. Objects coated with propulsion gel will become slippery, allowing them to slide across floors.
Conversion Gel[edit]
Any surface covered in this white gel will instantly become portalable, even if it wasn't before. Oftentimes you can use a conversion gel-coated surface to put more gel on another surface, using this method to spread gel all around the test chamber and put portals virtually anywhere you want.
Turrets[edit]
Now available to consumers!
The M.O. of turrets is simple: to shoot anything and everything that enters their line of sight. While a single shot won't be enough to kill you, getting shot enough will have you lying on the floor full of holes in short order. Oftentimes, you will need to find a way to either knock them over (thus disabling them) or drop them down holes or into goo. If all else fails, try and find a light bridge to at least protect you from their shots.
Crushers[edit]
Crushers do exactly what their name implies: they crush. Cubes, turrets, test subjects, they do it all. Naturally, you should stay as far away from them as possible. Stationary crushers will only kill you if you stand on them for too long, but moving crushers will kill you instantly. They appear primarily towards the end of the single-player campaign and in various places throughout co-op mode.